44 Aug. F. Focrste 



this feature) ; lateral and front margins bent over at nearly right angles with 

 the plane of the exterior of the valve. Shell slightly convex from the beak to 

 the extremities of the cardinal line, and about two-thirds of the distance from 

 the beak to the front, giving to the umbonal convex surface a subtriangular 

 form. More than half the area of the shell is bent suddenly over. Surface 

 covered by rounded radiating striae, a central and strong one more prominent 

 than the others ; about every fourth or fifth stria larger than the ones between ; 

 crossed by fine concentric lines. Striae increased by interstitial addition. Dor- 

 sal valve not observed. 



Width, measuring along the cardinal line, seven-eighths of an inch ; length 

 about the same. 



Position and locality — Cincinnati Group, near Boyd's station, on the Ken- 

 tucky Central Railroad, about 30 miles south of Cincinnati. 



Collected by U. P. James. 



In the James collection, preserved in the Walker Museum at 

 Chicago University, a series of specimens, numbered 2392, is 

 labelled as fonning the types of Rafinesquina declivis, James. Of 

 these, the specimen here represented on plate V by figures 12 A, B. 

 is regarded as the one originally described. It is characterized 

 by the sudden downward flexure of the lateral margins of the shell 

 resulting in a subtriangular form. It is this downward flexure 

 which suggested the term declivis. The choice of this term is 

 unfortunate since the strong downward curvature of the sides of 

 the shell and 'the triangular form of the specimen here regarded 

 as the one first described are due to the lateral compression and 

 contortion of the containing rock, a very argillaceous, fine-grained 

 limestone. All of the specimens belonging to the so-called series 

 of types evidently were obtained from the same locality, the rail- 

 road cut a quarter of a mile north of the station, where the massive 

 argillaceous limestone rises to a height of 25 feet above the rail- 

 road. This limestone lies directly below the base of the Eden 

 formation. Dahnanella vudtisccta and a species of Leptaena occur 

 within 1 1 feet of the base of the Eden. All of the specimens of 

 Rofiticsquina dccUvis in the series of types are characterized by the 

 prominence of the median striation, and by the distinctness of 

 every fourth, fifth or sixth one of the other radiating striae. 

 However, several of the specimens have the sides and anterior 

 portion only moderately deflected, and the specimen represented 

 by figure 12 D, and another specimen not figiu'ed, do not even have 

 the triangular form. In fact, figure 12 D probably represents the 

 normal, not distorted, form of Rafinesquina declivis, although some 

 of the specimens evidently were a little longer compared with the 



